Hand grippable bottle and preform

ABSTRACT

A preform having an annular wall region of increased wall thickness to produce a blow molded container having an annular concavity in a wall portion thereof to provide a hand grip feature, such a container when blow molded from such a preform and a carbonated beverage container having intaglio hand grip wall hand grip features.

This application claims the benefit of provisional application Ser. No.60/179,937 filed Feb. 3, 2000.

This patent application relates to preform designs for blow moldingplastic, e.g. polyethylene terephthalate (PET), containers having handgrip contour features and to containers having such features.

BACKGROUND OF THE INVENTION

In the past, different designs have been used to make a bottle meetspecifications. The typical failure for a bottle is in the grip area ordeep contour which will expand (creep) upon pressurization (carbonation)and/or higher than room temperatures. Typical bottle tests call for PETbottles to be pressurized to 4.0 volumes of CO₂ (˜55 psi at roomtemperature) and then placed in an oven for 24 hours at 100° F. At thistemperature, the gas pressure rises to ˜95 psi. In addition to thehigher forces applied to the plastic walls, the elastic modulus of theplastic is also slightly lower due to the higher temperature. Due togeometry, the bottles will creep in such a way distorting to the pointof eliminating any grip or contour design elements in the sidewall ofthe bottle.

Some geometric designs will resist the creep and try to retain theiroriginal shape, but generally a good percentage of the shape is lost.U.S. Pat. No. 5,803,290 shows one design that claims to hold asignificant portion of the shape.

SUMMARY OF THE INVENTION

The present invention is directed to making a hand grip or contourfeature perform in a large size container, and particularly to such acontainer for carbonated beverages, where a normal hand cannot grip thebottle with one hand and a prior art contour will not normally remainvisible under pressurized conditions. In addition, the inventionincreases the strength of the hand grip due to an increase in preformwall thickness even non-pressurized containers, such as liquor bottlesor hot-fill containers. The work that we have done indicates two newtechnologies. The first is the preform design and the second is thebottle design features that enhance the“gripability” and the retentionof“contour shape” of the bottle.

To make the bottle meet specifications, we place a ring of materialaround the Pinch Grip or Contour Feature of the bottle. To accomplishthat, the preform design is unique in that a ring of material is placedin approximately the middle of the preform so that upon stretching thethicker ring of material is located within the Pinch Grip area of thebottle or, in the case of a contour, in the inner contour geometry.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is a side elevation of a container for carbonated beverageshaving a waisted contour feature;

FIG. 2 is a side elevation of a container similar to that of FIG. 1illustrating a waisted contour feature;

FIG. 3A-D are, respectively, a sectional elevation and three sectionalcross-sections shown as 3B-3B, 3C-3C and 3D-3D in FIG. 3A of a preformfor blow molding the container of FIG. 1;

FIG. 4 is a diagrammatic cross-section of the container of FIG. 1 withthe preform of FIG. 3A superimposed therein to illustrate typical wallthicknesses of the container and material distribution of the preformduring blow molding;

FIG. 5 is a sectional elevation of a preform having the features of thepreform of FIG. 3A in combination with a base reinforcing ring;

FIG. 6 is a prior art, cross-sectional elevation illustrating thematerial distribution of a preform having a base reinforcing ring in theblow molding of footed (petaloid) container for carbonated beverages;

FIG. 7 is a prior art, diagrammatic underview of the container of FIG. 6illustrating the distribution of the reinforcing ring material in thefooted base;

FIG. 8 is a diagrammatic cross-section of an embodiment of a containerhaving hand grip features comprising an inverted petaloid design formedinto opposed areas of the container sidewall;

FIG. 9 illustrates the container of FIG. 8 shown in profile to show thehand grip features provided by the inverted petaloid design once thecontainer is pressurized; and

FIG. 10 is a view in the direction of arrow A in FIG. 8 illustrating thefeatures of a typical inverted hand grip feature.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reinforcing rings in preforms have been proposed in U.S. Pat. Nos.4,927,679 and 5,614,148. These reinforcing rings are located in the basearea of the preform (see FIGS. 6 and 7) and may be combined with thethickened panel sidewalls of the present invention, shown above in FIGS.3A-3D and in the combination, referred to above, in FIG. 5.

The preform of the present invention starts (FIG. 3A) from neck,shoulder portion and first wall portion with a normal or usual materialthickness, then transitions to a sidewall thickening ring, thentransitions back to a normal or usual wall thickness, or slightlygreater than this, but in all cases less thick than a base reinforcingring, if present (FIG. 5).

As can be seen from the drawings (FIGS. 3A and 5), the interior of thepreform has to taper inwards in order to remove the preform from typicalinjection molds. This inward taper means that the lower portions of thepreform have to stretch further for a typical design bottle. Because ithas to stretch further, the stretch ratios are higher for that sectionof the preform formed bottle. This is defined as the hoop stretch ratio(HSR). The HSR can be calculated from the OD of the preform wall, themiddle (avg) of the preform wall or the ID of the preform wall. Withoutan increase in the preform wall thickness in this area, the final bottlewall thickness will be less.

One could further add a base reinforcing ring design to this Pinch Grippreform where the wall section of the preform under the first thickeningring is approximately the initial wall thickness which then transitionsto a thickening rib which then transitions to a base area thinner thaninitial wall (see FIG. 5).

Note that the preform walls in the different sections may not be astraight wall but may have slight tapers which yield a non-uniform wallthickness in the vertical direction. In other words, FIG. 5 may have adifference in wall thickness from the top versus bottom. The same may befor the section immediately under the thickening rib. Where there aretapers in the wall thickness, it is common to calculate the HSR using anaverage wall thickness by averaging the thickest and thinnest sections.

The bottle geometry is important in that an indentation where one wouldput a grip feature (to hold in one's hand) is going to be a smallerdiameter than the corresponding main bottle diameter. This is also thecase with an inward contour feature. This changes the HSR. Please notethe two tables below to see how the wall thickness is impacted by theHSR with and without the indented grip.

TABLE I Wall thickness/Stretch Ratio to a Simple Cylinder Example:Location Example: Resultant on Range of Example: Hoop Bottle PreformPreform Wall Stretch Wall (FIGS. Wall Thickness Ratio (HSR) Thickness**3A & 5) Thickness Preform (in) *(ranges) (in) A = Typical t₁ .150 5.0.0100 Upper Body B = Transition C = (1.02 to 1.5) × 1.2 × .150 = 5.1.0118 Thickening t₁ .180 Rib D = Transition E = Typical t₂ .150 5.2.0097 Lower Body *Assumes Axial Stretch Ratio (ASR) Constant at 3.0**Wall thickness = preform wall thickness/(ASR × HSR)

TABLE 2 Wall Thickness/Stretch Ratio to an Indented Grip Feature orContour Feature Example: Location Example: Resultant on Range ofExample: Hoop Bottle Preform Preform Wall Stretch Wall (FIGS. WallThickness Ratio (HSR) Thickness** 3A & 5) Thickness Preform (in)*(ranges) (in) A = Typical t₁ .150 5.0 .0100 Upper Body B = Transition C= (1.02 to 1.5) × 1.2 × .150 = 3.0 .0200 Thickening t₁ .180 Rib D =Transition E = t₂ .150 5.2 .0097 Typical Lower Body *Assumes AxialStretch Ratio (ASR) Constant at 3.0 **Wall thickness = preform wallthickness/(ASR × HSR)

The only limitation to the % increase of the thickening rib is theallowable maximum wall thickness of the preform. There are limitationsto the absolute maximum wall thickness for quenching and reheating thicksections. Theoretically, the % increase could be several hundred percentbut the range noted in the tables is somewhat more practical.

If the “normal” preform (no thickened rib) was used on an indented gripor contour feature design as in Table 2, the resultant bottle wall wouldbe only .0167 inch [.150/(3*3)]. The thickening rib thus yields a 20%increase in wall thickness (0.020 vs. 0.0167) for an indented gripdesign and an 18% (0.0118 vs. 0.010) increase with simple cylinderdesign.

By itself, the thickening rib will increase the wall thickness of thebottle. In conjunction with an indented grip or contour feature thethickening rib will result in even thicker walls (by percentage). Thethickening rib allows thicker bottle wall in selected cross-sections ofthe bottle via preform design. This extra thickness minimized distortionthat will take place on an indented feature of a bottle when pressureand temperature are applied.

For a two-liter carbonated, soft drink bottle, the typical wallthickness in the label panel area is approximately 0.010-0.012 inch.Table 3 shows results of typical and thick rib preforms and resultantbottle wall thickness on an indented grip design plus the totaldistortion after pressurization and elevated temperature.

TABLE 3 Comparison of Typical and Thick Rib Preforms Blown into Grip orContour Feature Bottle Final Final Final Final Preform Preform BottleBottle Bottle Bottle Bottle Bottle Wall Wall Wall Wall Diameter DiameterHeights Heights Thickness Thickness Thickness Thickness Original UsingUsing Original using Using Preform Bottle Typical Thick Rib Typical RibBottle Typical Thick Rib Bottle Typical Thickened Vertical VerticalPreform Preform Preform Preform Diameter Preform Preform Heights PreformPreform Location Location (in) (in) (in) (in) (in) (in) (in) (in) (in)(in) upper upper 0.150 0.150 0.011 0.011 4.300 4.386 4.408 3.750 3.8253.788 body body thick rib grip 0.150 0.180 0.015 0.025 3.300 4.310 3.3833.000 3.300 3.030 lower lower 0.150 0.150 0.011 0.011 4.300 4.386 4.4083.750 3.825 3.788 body body

Turning now to FIG. 6, there is shown the petaloid base of the priorart.

FIG. 6 shows, in cross-section, part of monobase preform 18. The preform18, injection molded polyester, typically PET (polyethyleneterephthalate), is temperature conditioned and placed in a blow moldover and longitudinally stretched by a stretch rod 19. Pressurized gasis applied within the annular space 20 between the preform 18 andstretch rod 19 to push the walls of the preform 18 outwardly away fromthe axis 8 so as to expand the preform 18 into a desired finished shapein the blow mold which defines the exterior of that shape.

The preform comprises a neck finish, connected to a neck transitionportion by way of a neck support ring. A sidewall producing portion 20of the preform extends from the neck transition portion. Both the innerwalls 32 and outer walls 33 of the sidewall forming portion 22 areslightly tapered to facilitate release from the injection mold cavityand core. The sidewall forming portion 22 terminates in a closed baseproducing portion 23 having a wall thickness, in the gate producing areathereof, of 0.115 inch (2.921 mm). However, the transition (reinforcingring forming portion 24) between the sidewall forming portion 22 and thebottom forming portion 23 has an increased wall thickness of about 0.155inch (3.937 mm). The purpose of the reinforcing ring forming portion 24will be described hereinafter.

Prior to blow molding the preform 18 to produce the bottle 1, thepreform 18 is temperature conditioned with preform 18 being turned aboutaxis 8, during conditioning, so as to receive uniform heat. Thistemperature conditioning takes place outside the blow mold cavityimmediately prior to being positioned in the mold cavity. Forsimplicity, the neck producing portion (which remains substantially thesame) and the mold itself are not shown. The stretch rod 19, beingextendable along the longitudinal axis, is pushed downward stretchingthe preform longitudinally until the bottom 29 of the preform 18 isclosely adjacent (but spaced from) the bottom of the cavity. Thereinforcing ring forming portion 24 has a wall thickness greater thanboth the wall thickness of the sidewall forming portion 22 and thebottom forming portion 23 and therefor the reinforcing ring formingportion 24 has a greater mass per unit area and is slightly cooler thanthe thinner portions of the preform. Due to this and the greaterthickness, more stretching occurs in the sidewall forming portion 22 andthe gate area forming portion 23 than in the relatively cool thickerreinforcing ring forming portion 24. During blow molding, the stretchratio between the wall thickness of the gate area forming portion 23 andthe gate area 14 is about 2:1 whereas the stretch ratio between thesidewall forming portion 22 and the sloping wall 11 is about 12:1. InFIG. 6, the extension of the sidewall forming portion 22 by the stretchrod 19 occurs along axis 8 as shown by arrows 35 whereas arrows 36 showthe direction of extension in the bottom forming portion 23 by thestretch rod. The inside diameter of the preform 18 is greater than theoutside diameter of the stretch rod 19 whereby an annular space 20 isprovided. This space 20 facilitates pressurization of the preform 18 toproduce the bottle 1. Also, this space provides for a simply designedstretch rod having no step to accommodate the reinforcing ring formingportion 24 of the preform 18.

Pressurized gas is introduced within the preform 18 to blow the preform18 outwardly and downwardly away from the stretch rod to produce thebottle 1. The gas is introduced so that blow molding proceeds from thetop of the bottle 1 adjacent the neck transition to the bottom formingportion 23. The introduction of the gas may commence before the stretchrod has completed the longitudinal extension of the preform.

As is well known by those skilled in the art, preferred performance isobtained in PET containers by providing desired axial and hoopstretching of the material during the blow molding process thusbi-axially orienting the material of the container. The above describedcontrol of the temperature conditioning and the stretch rod operationcoupled with the blow molding itself provide desired bi-axialorientation of the container material together with accurate placementof the reinforcing ring forming portion 24 and gate area forming portion23 to form the reinforcing petaloid base of the container.

Finally, since the reinforcing ring forming portion 24 is cooler,material is pulled from bottom forming portion during blowing toincrease the stretch and thus the orientation in the gate area 14. Thisis believed at least in part because as the sidewall forming portion 22is blown outwardly away from the stretch rod 19, the gate area formingportion 23 is also blown outwardly and downwardly away from the stretchrod 19 while the slightly cooler more massive reinforcing ring formingportion 24 is laid into the pad forming portion of the mold last afterthe gate area has been formed. Thus, as ring area 24 is more resistantto expansion, the expansion of the reinforcing ring 24 has the tendencyto draw material from gate area 23 and area 22 adjacent the reinforcingring 24. Thus, the gate area forming portion 23 is able to expand acrossthe gate area with greater freedom than is available in the absence ofthe reinforcing ring forming portion 24.

When the blowing is complete, container in the form of a bottle isproduced having less weight than prior art petaloid based bottles whilemaintaining adequate strength to withstand internal pressure from acarbonated beverage.

The bottle illustrated includes a small annular lip 16, which isprimarily present for aesthetic purposes and for label alignment duringproduction. This lip lies adjacent the transition from the sidewall tothe base.

Turning now to FIG. 7, there is shown the bottom view of the base of thepresent invention showing the reinforcing ring 21 extendingcircumferentially around the base and following the curves and slopesthrough the foot walls 9, foot pads 10, straps 12 and sloping walls 11.

Referring now to FIGS. 8, 9, and 10, the hand grip features eachcomprise an intaglio feature in the form of five identical, hollow feet21′, which together form a petaloid foot formation with the feetsymmetrically and evenly disposed about the longitudinal axis of theintaglio feature. The innermost extensions of the feet 21′ terminate in“foot” pads 23′. The pads 23′ together define a plane disposed normal tothe axis 8′ of the hand grip feature, this axis 8′ passes through andextends normal to the longitudinal axis of the container. Each foot 21′comprises sloping sidewalls 24′ extending from its pad 23′to adjacentstraps 25′ which generally conform to the underlying modifiedhemispherical form. The container of FIGS. 8, 9 and 10 may be made usingthe preform of FIG. 3.

The dashed lines in the feet 21′ of FIG. 10 indicate the theoreticalunderlying intersections of the surfaces defining the feet and themodified hemispherical shaped base. These intersections are theoreticaldue to the joining of the surfaces by smooth transitions, fillets orchamfers in order to define the curvature of the surfaces concerned.

The radially extending straps 25′ are disposed between adjacent pairs offeet 21′. These straps 25′ each include flat strap, root portions 26′but otherwise substantially follow the surface curvature of theunderlying modified hemispherical shape of the base. The straps 25′ eachterminate at and open into an extended portion and meet a sloping wall.

The base area 27′ through which extends the axis is connected to eachpad 23′ by a ridge ankle 28′ joined on either side by blending curves toportions of the sloping walls 24′.

Although shown by solid lines, for simplicity, at the junctions betweenthe sloping sidewalls 24′ and the straps 25′ and pads 23′, and betweenthe ankles 28′ and base area 27′, the intersection of these elements arecurved in cross-section to provide smooth transitions to and structuralrigidity.

Although described in detail with reference to carbonated beveragecontainers, it will be appreciated that the present invention hasapplication for use in non-pressurized containers which would otherwiseyield due to gripping forces.

1. A preform for blow molding container having a hand grip feature tofacilitate handling of the container, the preform having a hollowinterior for blow molding the container having a hand grip feature tofacilitate handling of the container, the preform defining alongitudinal axis and comprising an integral structure, the hollowinterior of which is snaped and sized to allow axial removal of thepreform from a core of an injection mold in which the preform is molded,the preform having, in interconnected axial sequence, a container neckfinish forming portion defining an opening to the hollow interior, anannular container shoulder forming portion, an annular container firstwall forming portion, an annular container intermediate wall formingportion, an annular container second wall forming portion and a closedcontainer base forming portion, wherein the annular intermediate wallforming portion has a wall thickness greater than the first and thesecond annular wall portions.
 2. The preform according to claim 1,wherein the closed base forming portion defines an annular basereinforcing ring of a wall thickness greater than a wall thickness ofthe first and second wall forming portions and greater than a wallthickness of a remainder of the closed container base forming portion.3. A blow molded container having a contour feature to facilitatehandling of the container, the preform having a hollow interior for blowmolding the container having the contour feature, the preform defining alongitudinal axis and comprising an integral structure, the hollowinterior of which is shaped and sized to allow axial removal of thepreform from a core of an injection mold in which the preform is molded,the preform having in interconnected axial sequence, a container neckfinish forming portion defining an opening to the hollow interior, anannular container shoulder forming portion, an annular container firstwall forming portion, an annular container intermediate wall formingportion, an annular container second wall forming portion and a closedcontainer base forming portion, wherein the annular intermediate wallportion has a wall thickness greater than the first end the secondannular wall portions, the blow molded container having, ininterconnected axial sequence, a neck finish formed by the neck finishof the preform, a shoulder portion formed from the shoulder portion ofthe preform, first, intermediate and second wall portion formed from thefirst, intermediate and second wall portions of the preform and a closedbase formed from the dosed base portion of the preform, the contourfeature comprising an annular concavity in the intermediate wall portionof the preform, the annular concavity having a wall thickness greaterthan the wall thickness of the first and second wall portions of theblow molded container.